This invention relates to forage harvesters of the type having a rotary reel cutterhead and a feed roll mechanism for delivering crops thereto to obtain a uniform length of cut and, more particularly, to an improved driving arrangement for the feed roll mechanism.
Two important characteristics which are desirable in a forage harvester feed roll drive are the capability to provide a reverse drive for clearing blockages, as well as forward and neutral drives, and the ability to remotely actuate the shifting of the drive from one drive condition to another. The latter becomes increasingly important with the trend to enclosed tractor cabs dictated by increasingly lower noise level requirements.
In the past, feed roll drives for forage harvesters have generally included a mechanical transmission having a gear type shifting mechanism enclosed in a gearbox and a gear or chain speed reduction for driving the feed rolls in forward, neutral, and reverse. The transmission is usually driven from the cutterhead drive to provide a fixed speed ratio, which may be varied by changing sprockets in the chain drive, to produce uniform lengths of cut. Such a mechanical transmission is illustrated, for example, in Long et al. U.S. Pat. No. 3,739,559 and numerous others. It is also known to provide remote control for these mechanical transmissions, generally a mechanical linkage or a hydraulic cylinder, which may be electrically actuated, controlled from the tractor cab and controlling a shifting lever on the gearbox. While these feed roll drives accomplish their intended ends, they can also be costly.
Accordingly, it is an object of the invention described and claimed herein to provide an improved forage harvester feed roll drive mechanism which will provide forward, neutral, and reverse drives and remote control while being less expensive than the conventional transmission.
It is a more specific object to provide an improved feed roll drive mechanism wherein an open chain drive is combined with a pair of electric clutches to produce forward, reverse, and neutral drive conditions and a convenient means for remotely controlling the shifting from one condition to the other.
It is a further specific object of the invention to provide such a forage harvester feed roll drive means wherein the reversing gearbox is eliminated.
These and other objects of the invention are met in a forage harvester having a rotary reel cutterhead, a feed roll mechanism for feeding crops to the cutterhead, and drive means for the feel roll mechanism including a forward chain drive mechanism incorporating intermediate shafts and an electromagnetic clutch and a reverse chain drive mechanism incorporating a second electromagnetic clutch, both drive mechanisms being driven from a common input shaft which also drives the cutterhead and driving a common output shaft, the output shaft being operatively connected with the feed roll mechanism, and electrical remote control means for operating the electromagnetic clutches for mutually exclusive engagement or with neither clutch engaged.
Among the advantages of such a drive mechanism are the simplicity of control of the drive mechanism and the elimination of the gearbox which becomes practical with the elimination of the gear shifting mechanism of the prior art transmissions.
A further advantage of the feed roll drive mechanism presented herein is that less severe impact loading on the drive mechanism during shifting will occur, especially when shifting directly from forward to reverse, than the impact loadings experienced with a gear shifting mechanism, particularly one using a gear type speed reducing mechanism as well. Drive chains have a tendency to flex somewhat when tensile loads are imposed. While the period over which this occurs is indeed brief, it still tends to extend the period of pickup of the load over that occurring in a gear mechanism. Moreover, forage harvester drives are commonly provided with jaw clutch mechanisms for picking up the load or, in the case of the Long et al. patent, a reversely spinning gear which engages another gear. In either case, the drive coupling is immediately positive whereas with electromagnetic clutches, there is some slippage as the load is picked up which again extends the interval over which the mechanism is loaded, thus reducing impact loads and extending the life of the various drive elements .